Involvement in social relationships is associated with better mental health, better physical health, and reduced risk for mortality. The marital relationship is the most important relationship in this regard. The quality of relationships is also important for health-with supportive relationships having salutary effects on health and strained relationships adversely affecting health. These are well-established findings in the research literature, yet we know very little about how the marital relationship changes over the life course or how the impact of marital quality on health varies over the life course. Marital quality/dynamics may become more important to individuals later in the life course as the marital relationship becomes more central to their lives and as physical health problems become more prevalent. Specific aims for the proposed project include: (1) Determine how multiple facets of marital quality (both positive and negative) change over the life course, (2) determine how these facets of marital quality affect mental health, physical health, and health behavior and how these effects may change over the life course, (3) consider the role of mediating (e.g., health behavior) factors in affecting the relationship between marital quality and physical health, (4) conduct a qualitative analysis of processes underlying marital quality change and the impact of marital quality on well-being, and (5) consider gender differences in the dynamics and consequences outlined in Aims 1-4. We work from a life course perspective and will use longitudinal data from a national 3-wave panel survey (conducted in 1986, N=3,617, 1989, N=2,867, 1994 N=2,398) to address Aims 1-3 and 5. We also plan to conduct in-depth interviews with 10 married individuals in six age cohorts (N=60) to complete Aim 4. This qualitative component will focus on individuals' perceptions of change in marital dynamics over time as well as the processes through which these dynamics affect subjective well being.